Active modular aerodynamic drag reduction system

ABSTRACT

Systems and methods for airflow control of a moving ground vehicle are provided. The system includes an actuator module and a sensor unit mounted on the vehicle, and a controller. The actuator module includes at least one synthetic jet actuator to generate a synthetic jet, to modify an airflow around the vehicle. The sensor unit includes at least one environment sensor to capture environmental sensor data proximate the vehicle. The controller receives the environmental sensor data from the sensor unit and determines at least one of a drive frequency and a drive amplitude for controlling the at least one synthetic jet actuator, based on the received environmental data.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/647,153, filed May 26, 2015 which is the U.S. National PhaseApplication of PCT/US2014/016809, filed Feb. 18, 2014, which claims thebenefit of U.S. Provisional Application No. 61/766,193 entitled ACTIVEMODULAR AERODYNAMIC DRAG REDUCTION SYSTEM, filed on Feb. 19, 2013, thecontent of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to the control of airflow for groundvehicles, more specifically to airflow control systems and methods usingsynthetic jet actuators to reduce aerodynamic drag of moving groundvehicles.

BACKGROUND OF THE INVENTION

Various solutions exist for improving the aerodynamic properties ofmoving bluff-shaped ground vehicles (i.e., non-streamlined shapedvehicles such as cars, trains, trucks, land-carried intermodalcontainers, etc.). When the ground vehicle travels, the bluff-shapedbody may produce considerable aerodynamic resistance. Typically, aregion of separated airflow occurs over a large portion of the surfaceof the bluff body. This may result in a high aerodynamic drag force anda large wake region. Airflow around the vehicle typically exhibitsunsteadiness, such as periodic vortex formation and shedding. To reducethe known drawbacks of the vehicle shape, airflow control systems may beused to improve the aerodynamics.

Many current aerodynamic drag reduction devices are based on modifyingthe form of the vehicle body, its geometry, its surfaces or the type ofbody material to reduce the drag force exerted on the vehicle body.Other current aerodynamic drag reduction systems use pneumaticaerodynamic control to reduce flow separation. Typically, externallysupplied compressed air is used to produce an additional flow of airthrough blowing outlets, such as openings on the vehicle. These systemsuse a compressed air plenum for all of the blowing outlets. Thecompressed air is discharged from the blowing outlets to reduce flowseparation and reduce drag. Because the systems use a compressed airplenum for all blowing outlets, the system is connected to a robust airsupply resource, such as the vehicle air supply/generation system or toa mountable compressor that is independent of the vehicle. Thedependency on compressed air may substantially increase the energyrequirements of the system, and may increase the size and/or weight ofthe system at the expense of the carrying capacity of the vehicle.

SUMMARY OF THE INVENTION

One aspect of the present invention relates to a system for airflowcontrol of a moving ground vehicle. The system includes an actuatormodule mounted on the vehicle, a sensor unit mounted on the vehicle anda controller. The actuator unit includes at least one synthetic jetactuator configured to generate a synthetic jet, to modify an airflowaround the vehicle. The sensor unit includes at least one environmentsensor configured to capture environmental sensor data proximate thevehicle. The controller is configured to receive the environmentalsensor data from the sensor unit and to determine at least one of adrive frequency and a drive amplitude for controlling the at least onesynthetic jet actuator, based on the received environmental data.

Another aspect of the present invention relates to a method for airflowcontrol of a moving ground vehicle. The method includes capturingenvironmental sensor data proximate the vehicle from an environmentalsensor mounted on the vehicle; determining, by a controller, at leastone of a drive frequency and a drive amplitude for controlling at leastone synthetic jet actuator mounted on the vehicle, based on the receivedenvironmental data; and generating a synthetic jet by the at least onesynthetic jet actuator based on the at least one of the drive frequencyand the drive amplitude, to modify an airflow around the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood from the following detailed descriptionwhen read in connection with the accompanying drawings. It is emphasizedthat, according to common practice, various features/elements of thedrawings may not be drawn to scale. On the contrary, the dimensions ofthe various features/elements may be arbitrarily expanded or reduced forclarity. Moreover, in the drawings, common numerical references are usedto represent like features/elements. Included in the drawing are thefollowing figures:

FIG. 1A is a functional block of an exemplary airflow control system fora bluff-body shaped ground vehicle, according to an embodiment of thepresent invention;

FIG. 1B is a functional block diagram of the power manager shown in FIG.1A, according to an embodiment of the present invention;

FIG. 2A is a perspective view diagram of a tractor including anexemplary actuator module and jet-angle controlling fairing device,according to an embodiment of the invention;

FIG. 2B is a perspective view diagram of an inset portion of the tractorshown in FIG. 2A, according to an embodiment of the present invention;

FIGS. 3A, 3B and 3C are top view diagrams of a portion of the tractorshown in FIG. 2A, illustrating airflow control with the jetangle-controlling fairing device shown in FIG. 2A when the tractor isnot connected to a trailer and when the tractor is connected to atrailer, respectively, according to embodiments of the invention;

FIG. 4A is a perspective view diagram of a trailer including anexemplary actuator module positioned on the trailer, according to anembodiment of the invention;

FIG. 4B is a perspective view diagram of an inset portion of the trailershown in FIG. 4A, illustrating exemplary components of the actuatormodule shown in FIG. 4A, according to an embodiment of the invention;

FIG. 5A is an exploded perspective view diagram of an exemplaryactuator, according to an embodiment of the invention;

FIGS. 5B and 5C are perspective view diagrams of the actuator shown inFIG. 5A, according to an embodiment of the invention;

FIGS. 6A and 6B are cross-section diagrams of a portion of the actuatorshown in FIG. 5C, illustrating actuation of the actuator, according toan embodiment of the invention;

FIGS. 7A and 7B are perspective view diagrams of a tractor coupled to atrailer and the resultant airflow in the tractor gap without operationof an exemplary airflow control system and with operation of the airflowcontrol system, respectively, according to embodiments of the invention;

FIGS. 7C and 7D are perspective view diagrams of a trailer and theresultant airflow at the back of the trailer without operation of anexemplary airflow control system and with operation of the airflowcontrol system, respectively, according to embodiments of the invention;

FIG. 8 is a flow chart illustrating an exemplary method of controllingairflow of a bluff-body shaped vehicle, according to an embodiment ofthe invention;

FIG. 9 is a flow chart illustrating an exemplary method of performingdiagnostic control of an airflow control system, according to anembodiment of the invention;

FIG. 10 is a flow chart illustrating an exemplary method of performingjet angle control of a jet angle-controlled fairing, according to anembodiment of the invention;

FIG. 11 is a flow chart illustrating an exemplary method for controllingthe stability of the vehicle, according to an embodiment of theinvention; and

FIGS. 12A and 12B are flow charts illustrating exemplary methods forperforming spray control using one or more actuators of the airflowcontrol system shown in FIG. 1A, according to embodiments of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Aspects of the invention relate to methods and airflow control systemsfor reducing aerodynamic drag on a moving bluff-body shaped groundvehicle using active flow control actuators. According to an exampleembodiment, the system includes modular actuator components that may beremovably mounted on the vehicle. The actuator components may beindependent (i.e., structurally independent and mechanicallyindependent) from the vehicle upon which they are mounted and may notrequire any modifications to the vehicle body.

An exemplary airflow control system may include an actuator modulehaving at least one synthetic jet actuator, a sensor unit having atleast one sensor for capturing environmental data proximate to thevehicle and a controller. The controller is configured to analyze theenvironmental sensor data and control operation of the actuators(including the operating voltage amplitude and the operating voltagefrequency) based on the environmental sensor data. The actuator modulemay be an aerodynamically shaped unit and multiple actuator modules mayoperate independently from each other. The actuator modules may bemounted directly on the vehicle body or may be mounted on the vehiclebody via a mounting frame. According to another example, the actuatormodules may be integrated into the vehicle body or may be integrated ina fairing.

Exemplary synthetic jet actuators use the airflow proximate the actuatorto create an oscillating flow of air (i.e., a synthetic jet), responsiveto an input voltage signal via the controller. Because the actuatormodules do not use an external air supply, they can be mounted at anydesired location on the vehicle body. Spacing between actuator modules,the number of actuator modules and a position of each actuator module onthe vehicle body may be altered. Thus, the airflow control system may beadaptable to a wide range of ground vehicles. Because the actuatormodules may be replaceable (i.e., removably coupled to the vehicle body)and are mounted to the vehicle body (as opposed to being part of thevehicle body), the actuator modules may be easily replaced in case ofmechanical failure. The ability to change the number and location of theactuator modules also allows the airflow control system to be tailoredto the user's specific needs (and thus allows more control over whereand how much aerodynamic drag reduction is provided).

In contrast, current aerodynamic drag reduction systems having activeflow control techniques use externally supplied compressed air. Thecurrent systems are also integrated into the vehicle body and are builtaround a centralized shaft. The flow is generated through openings inthe main air supply shaft in such a way that the components of thesystem depend and affect each other. Due to this dependence, the entiresystem operates as one large and complex object with limited flexibilityin its installation and limited configurability. This lack offlexibility and dependence on the vehicle body for the air supply mayreduce the system's energy efficiency, increase its manufacturingcomplexity and limits the system's applicability to a wide range ofmoving bodies.

Referring to FIG. 1A, a functional block diagram of an example airflowcontrol system 102 mounted on vehicle 100 is shown. System 102 mayinclude sensor unit 104, controller 106, power manager 108, one or moreactuators 110, driver interface 116 and storage 118. System 102 mayoptionally include one or more of fairing servomotor 112 and jetangle-controlling fairing device 114.

Vehicle 100 may include any bluff-shaped ground vehicle (i.e., anyvehicle that is not an air vehicle). Vehicle 100 may include, withoutbeing limited to, cars, trains, trucks, land-carried intermodalcontainers, etc. Trucks may include a tractor or a tractor with one ormore trailers (such as a tandem trailer).

Sensor unit 104 may include one or more environment sensors 120 and oneor more velocity sensors 122 to collect sensor data proximate vehicle100. Environment sensor 120 may include, for example, without beinglimited to, a temperature sensor, a humidity sensor or a rain sensor.Velocity sensor 122 may include, without being limited to, a speedometeror a relative wind speed sensor. More than one environment sensor 120and/or velocity sensor 122 may be positioned on vehicle 100.

Sensor unit 104 may also include one or more diagnostic sensors 124,such as, without being limited to, current detectors and/or straingauges to identify electrical problems (such as short circuits) and/ormechanical problems with actuators 110. Identified electrical and/ormechanical problems of actuators may be communicated to the driver viadriver interface 116. In some examples, the identified problems maycause system 102 to cease operation. In other examples, the identifiedproblems may be automatically corrected (or at least an automaticattempt to correct the problems may be made) during operation of system102.

Sensor unit 104 may also, optionally, include one or more proximitysensor 126 and/or one or more stability sensors 128 (for example, suchas center of gravity sensor, a weight sensor or an accelerometer). Forexample, if vehicle 100 is a tractor trailer, proximity sensor(s) 126may be used to determine a proximity of the trailer to the tractor. Asanother example, if vehicle 100 includes more than one trailer,proximity sensor(s) 126 may determine a proximity between the trailers.Stability sensor(s) 128 may be used to determine whether movement of thetrailer body indicates that it is becoming unstable.

Controller 106 may receive sensor data from sensor unit 104 in order toperform drag reduction control 130 and diagnostic control. The receivedsensor data may also be used to perform optional fairing jet anglecontrol 134, optional stability control 136 and/or optional spraycontrol 138.

Controller 106 may be configured to control operation of one or moresensor unit 104, power manager 108, actuators 110, optional fairingservomotor 112, optional fairing device 114 and driver interface 116.Controller 106 may include, for example, a logic circuit, a digitalsignal processor, a microcontroller or a microprocessor.

Controller 106 may be configured to perform drag reduction control 130,to control the operating frequency and operating voltage amplitude ofthe electrical signal provided to actuators 110, based on theenvironmental conditions proximate vehicle 100. To determine theenvironmental conditions, controller 106 may use the sensor datareceived from environment sensors 120, as well as sensor data fromvelocity sensor 122. The operating frequency and voltage amplitude maybe determined according to a predetermined relationship betweenenvironmental conditions, relative flow-vehicle velocity and optimalactuator voltage and frequency.

Drag reduction control 130 may be performed when vehicle 100 is movingabove a predetermined velocity threshold. To identify the velocity ofvehicle 100, controller 106 may use the sensor data received fromvelocity sensor 122. A description of drag reduction control 130 isprovided further below with respect to FIG. 8.

Controller 106 may also be configured to perform diagnostic control 132,to determine whether components of system 102 are operating under normalconditions. For diagnostic control 132, controller 106 compares sensordata received from diagnostic sensors 124 to predetermine conditions, toidentify electrical and/or mechanical problems with components of system102 or to confirm that system 102 is operating under normal conditions.Depending upon the operating conditions, controller 106 may provide anindication of a normal or faulty condition to driver interface 116.Diagnostic control 132 is described further below with respect to FIG.9.

Controller 106 may be configured to perform optional fairing jet anglecontrol 134 (when system 102 includes optional jet angle-controllingfairing device 114). As described further below in FIGS. 3A and 3B,fairing device 114 may be pivotably attached to vehicle 100 and may haveone or more actuators 110 mounted thereon. The position of fairingdevice 114 may be changed, for example, based on whether a trailer isattached to a tractor. Changing the position of fairing device 114changes a jet angle of the synthetic jet (described further below withrespect to FIGS. 6A and 6B) that is output by actuators 110. Theposition of fairing device 114 may be changed manually. According toanother embodiment, system 102 may include optional fairing servomotor112, to automatically change the position of fairing device 114, basedon fairing jet angle control 134. Fairing jet angle control 134 isdescribed further below with respect to FIG. 10.

Controller 106 may be configured to perform optional stability control136. Stability control 136 may be useful, for example, to monitor andadjust movement of a trailer attached to vehicle 100 (such as when thetrailer is moving in an unstable manner). In stability control 136,controller 106 may receive stability sensor data from stability sensors128, and may determine whether movement of vehicle 100 is according to apredetermined stable condition. If controller 106 determines thatvehicle 100 is not moving in a stable condition, controller 106 may senda control signal to power manager 108 to activate one or more actuators110 to produce a stabilizing net force on vehicle 100. Stability control136 is described further below with respect to FIG. 11.

Controller 106 may be configured to perform optional spray control 138.For spray control 138, controller 106 may receive sensor data fromenvironment sensors 120 (such as a rain sensor), to determine whetherrain is detected. When controller 106 detects rain, controller 106 maysend a control signal to power manager 108 to control one or moreactuators 110. The selected actuators 110 may produce synthetic jets toredirect rain away from vehicle 100 and/or to redirect the spray awayfrom its exposure by other vehicles that are behind or next to vehicle100. Spray control 138 is described further below with respect to FIGS.12A and 12B.

Driver interface 116 may include any suitable interface to providevisual and/or audio indication of a normal or faulty operatingcondition. Driver interface 116 may be provided in a vehicle cabin ofvehicle 100, for the driver's convenience. As another example, driverinterface 116 may be provided on controller 106 and/or power manager108. For example, driver interface 116 may be an external unit mountedon a component of system 102 or may be formed as part of a component ofsystem 102. Responsive to the indication on driver interface 116, thedriver may operate vehicle 100 or may have system 102 inspected formaintenance issues.

System 102 may include storage 118. Storage 118 may store one or morevalues for sensor unit 104, controller 106, power manager 108, actuators110, fairing servomotor 112, fairing device 114 and/or driver interface116. Storage 118 may include, for example, a random access memory (RAM),a magnetic disk, an optical disc, flash memory or a hard drive.

Power manager 108 may be configured to receive control signals fromcontroller 106 and activate one or more actuators 110 according tooperation parameters (frequency and voltage amplitude) provided bycontroller 106 in the control signal. Power manager 108 is describedfurther below with respect to FIG. 1B.

Each actuator 110 may be configured to receive an electrical signal(having an operation frequency and an operation voltage amplitude) frompower manager 108 and may produce a synthetic jet. The synthetic jetsproduced by actuators 110 may be used to control the airflow aroundvehicle 100. The synthetic jets of actuators 110 may also be used toprovide optional stability control of vehicle 100 and/or optional spraycontrol under rain conditions. Actuators 110 may be mounted directly tovehicle 100 or may be mounted to vehicle 100 via a mounting frame, suchas mounting frame 208 shown in FIG. 2B. As another example, actuators110 may be formed integral with the vehicle body and/or integral withfairing device 114. Actuators 110 are described further below withrespect to FIGS. 5A-5C and FIGS. 6A and 6B.

It is understood that components of one or more of sensor unit 104,controller 106, power manager 108, driver interface 116 and storage 118may be implemented in hardware, software or a combination of hardwareand software.

Referring to FIG. 1B, a functional block diagram of an exemplary powermanager 108 is shown. Power manager 108 may include direct current(DC)/DC converter 142, one or more amplifiers 144 and one or more signalgenerators 146. DC/DC converter 142 may receive a voltage signal fromvehicle battery 140 and convert the voltage to a voltage range suitablefor actuators 110 (as well as being suitable for amplifier(s) 144).Power manager 108 may also receive control signal 148 from controller106 indicating an operation frequency and operation voltage amplitudefor actuators 110. In FIG. 1B, N number of electrical signals 150 (whereN is an integer greater than or equal to 1) having the frequency andvoltage amplitude indicated by control signal 148 are supplied toactuators 110. The N number of electrical signals 150 may correspond toN number of actuators 110 or may correspond to groups of actuators (suchas actuators arranged in different actuator modules 202 (shown in FIG.2A). Each actuator in the group may receive the same electrical signal.Thus, different electrical signals 150 may be provided to differentgroups of actuators (i.e., different actuator modules 202).

The control signal 148 from controller 106 may also indicate specificactuators 110 for activation with the corresponding operationparameters. Responsive to the control signal, signal generators 146 maygenerate a voltage signal having an oscillation frequency correspondingto the operation frequency received in control signal 148. Amplifiers144 may amplify the generated signal from signal generator 146 accordingto the voltage amplitude received in control signal 148 from controller106. Power manager 108 may send a generated electrical signal 150 withthe operation frequency and voltage amplitude to selected actuators 110.

Referring next to FIGS. 2A and 2B, perspective view diagrams of anexample system 102 mounted on vehicle 200 is shown. In particular, FIG.2A is a perspective view diagram of tractor 200 and FIG. 2B is aperspective view diagram of inset 206 of FIG. 2A.

In FIGS. 2A and 2B, a plurality of actuators 110 are disposed inactuator module 202. In the example, actuator module 202 is mounted onfairing device 114. As shown in FIG. 2B, fairing device 114 ispivotable, as illustrated by arrow 214. FIG. 2B also illustrates exampleplacement of sensor unit 104, controller 106 and power manager 108 ontractor 200.

Although FIG. 2A illustrates one actuator module 202 disposed on fairingdevice 114, at position 204-1, actuator module 202 may be mounted at anyother suitable positions on tractor 200. Accordingly, FIG. 2A alsoillustrates other example positions for actuator module 202 (and/orindividual actuators 110) on tractor 200. For example, actuator module202 (or actuator 110) may be mounted at position 204-2 (on the roof),position 204-3 (on the mirror), position 204-4 (on the front skirt),position 204-5 (on the front wheel) and/or position 204-6 (on thetractor back wheel). The positions shown in FIG. 2A are examples. It isunderstood that actuator module 202 and/or actuators 110 may bepositioned at any other suitable location on tractor 200.

Actuators 100 may be disposed in housing 210 on mounting frame 208.Housing 210 may be configured in any geometry and/or formed of anysuitable materials to reduce drag force exerted on actuator module 202.Although not shown in FIG. 2B, mounting frame 208 may include anelectrical conduit (such as electrical conduit 410 shown in FIG. 4B), toelectrically connect actuators 110 to power manager 108. As shown inFIG. 2B, actuators 110 generate synthetic jets 212 which may be used tocontrol the airflow and reduce aerodynamic drag on tractor 200.

Referring next to FIGS. 3A-3C, positioning of fairing device 114 tocontrol the synthetic jet angle of actuators 110 (on actuator module 202shown in FIGS. 2A and 2B) is described. In particular, FIG. 3Aillustrates fairing device 114 in a first position when no trailer isattached to tractor 200; FIG. 3B illustrates fairing device 114 in asecond position when a trailer is attached to tractor 200; and FIG. 3Cillustrates fairing device 114 in another example position when atrailer is attached to tractor 200. As shown in FIG. 3A, positioningfairing device 114 inwards towards a trailer gap (between tractor 200and a front surface of a trailer, such as trailer 400 shown in FIG. 4A)produces synthetic jets 212 at an angle 301 (with respect to thehorizontal direction). When synthetic jets 212 are positioned at theangle 301 shown in FIG. 3A, this causes airflow 300 around tractor 200to be pulled toward the center of the tractor gap (as airflow 302).

As shown in FIG. 3B, when fairing device 114 is positioned away from thetractor gap (parallel to the horizontal direction), synthetic jets 212cause airflow 300 to be directed parallel to the horizontal direction(as airflow 304). Airflow 304 may reduce aerodynamic drag on a trailerportion attached to tractor 200 (not shown).

FIGS. 3A and 3B illustrate two example positions of fairing device 114.Fairing device 114 may also be positioned as shown in FIG. 3C, at anoutward angle 303 relative to the horizontal direction. When fairingdevice 114 is positioned at outward angle 303, synthetic jets 212 causeairflow 300 to be directed away from the trailer gap (as airflow 306).

Referring to FIGS. 4A and 4B, an example of system 102 as mounted ontrailer 400 is shown. In particular, FIG. 4A is a perspective viewdiagram of trailer 400 including system 102; and FIG. 4B is aperspective view diagram of inset 406 of FIG. 4A. FIG. 4B alsoillustrates example placement of sensor unit 104 and controller 106 ontrailer 400. Power manager 108 may be disposed in another location, suchas the location shown in FIG. 2B.

In FIGS. 4A and 4B, actuators 110 are disposed in actuator module 402positioned at location 404-1 on the rear of trailer 400. Location 404-1represents one example position for actuator module 402. Actuator module402 (or individual actuators 110) may also be positioned at otherlocations such as, without being limited to, location 404-2 (at thetrailer back wheel), location 404-3 (on a side of the trailer), location404-4 (on a roof of trailer 400), location 404-5 (at a front of trailer400) and location 404-6 (at a bottom of trailer 400).

As shown in FIG. 4B, actuator module 402 may include mounting frame 408having electrical conduit 410. Electrical conduit 410 may electricallycouple actuators 110 to power manager 108. Actuator module 402 may alsoinclude housing 412 in which actuators 110 are disposed. Actuators 110may produce synthetic jets 212 in accordance with their positioning inhousing 412. Similar to housing 210 (FIG. 2B), housing 412 may be formedof any suitable geometry and/or any suitable material to reduce a dragforce exerted on actuator module 402.

Referring to FIGS. 5A-5C, an example of actuator 110 is shown. Inparticular, FIG. 5A is an en exploded perspective view diagram ofactuator 110; and FIGS. 5B and 5C are perspective view diagrams ofactuator 110.

Actuator 110 is a synthetic jet actuator including outer frame 502-1,502-2 enclosing actuator cartridge 518. As shown in FIG. 5C, actuatorcartridge 518 may be slidably disposed within outer frame 502, for easyaccess and interchangeability (such as when a problem is detected with aspecific actuator 110). Actuator cartridge 518 may include electricalconnector 516 for receiving electrical signal 150 (FIG. 1B) from powermanager 108.

Actuator cartridge 518 includes housing 510 having cavity 512 (formed byside wall 520). The housing 510 and cavity 512 may take any suitablegeometric configuration, including the configuration shown in FIG. 5A.Housing 510 also includes jet orifice 514. Housing 510 may bemechanically coupled to plates 506-1, 506-2, each having respectivepiezoelectric discs 508-1, 508-2. Piezoelectric disc 508-1, side wall520 and piezoelectric disc 508-2 may define cavity 512 filled with afluid (such as air). Cavity 512 may be configured to be in fluidcommunication with jet orifice 514. Jet orifice 514 may be formed of anysuitable geometric shape.

Each piezoelectric disc 508 may include a piezoelectric material and maybe electrically connected to power manager 108 (FIG. 1B). Power manager108 may be configured to apply an excitation voltage to eachpiezoelectric disc 508-1, 508-2, to displace each piezoelectric disc.The excitation voltage applied to piezoelectric discs 508-1, 508-2 maybe an oscillating signal having an oscillation frequency and anamplitude (selected by controller 106 according to the environmentalconditions and relative velocity). Thus, piezoelectric discs 508 may beperiodically displaced inwardly and outwardly relative to cavity 512,and force fluid in and out of jet orifice 514.

Outer frame 502 may include perforated sheet 504. Perforated sheet 504may permit movement of piezoelectric disc 508 within outer frame 502,while reducing fluid loading on piezoelectric disc 508 (external toactuator cartridge 518). For example, by allowing piezoelectric disc 508and outer frame 502 to be in fluid communication with ambient fluidthrough perforated sheet 504, fluid external to actuator cartridge 518may be more easily displaced by piezoelectric disc 508 into the ambientenvironment.

Although FIGS. 5A-5C illustrate actuator 110 having two piezoelectricdiscs 508-1, 508-2, actuator 110 may also be configured with onepiezoelectric disc 508. For example, only plate 506-1 may includepiezoelectric disc 508-1. Plate 506-2 may not include a piezoelectricplate, but, rather, may be a rigid structure. The excitation voltageapplied to piezoelectric disc 508-1 may cause piezoelectric disc 508 tobe periodically displaced, to force fluid in and out of jet orifice 514.

Referring to FIGS. 6A and 6B, cross-section diagrams of actuatorcartridge 518 along line A-A (FIG. 5C) are shown, illustrating operationof actuator cartridge 518 (to form synthetic jet 602). FIG. 6A depictsactuator cartridge 518 as piezoelectric discs 508-1, 508-2 arecontrolled (by electrical signal 150) to move inward into cavity 512, asdepicted by arrows 610. Cavity 512 has its volume decreased and fluid isejected through the jet orifice 514. As the fluid exits cavity 512through jet orifice 514, the flow separates at the edges of jet orifice514 and creates vortex sheets 604 which roll into vortices 606 and beginto move away from jet orifice 514, to form synthetic jet 602.

FIG. 6B depicts actuator cartridge 518 as piezoelectric discs 508-1,508-2 are controlled (by electrical signal 150) to move outward withrespect to cavity 512, as depicted by arrow 612. Cavity 512 has itsvolume increased and ambient fluid 600 rushes into cavity 512. Whenpiezoelectric discs 508-1, 508-2 move away from cavity 512, vortices 606are already removed from the jet orifice edge and thus are not affectedby ambient fluid 600 being drawn into cavity 512. In addition, a jet ofambient fluid 602′ is synthesized by vortices 606 creating strongentrainment of ambient fluid 600 drawn from large distances away fromjet orifice 514.

Referring generally to FIGS. 5A-5C and FIGS. 6A and 6B, actuators 110may actively use the moving air (ambient air 600) around the vehiclebody to generate a controlled pulsating flow of air (synthetic jet 602).Synthetic jet 602 may be used to manipulate the boundary layer aroundthe body. Actuators 110 operate under electrically power (by electricalsignal 150), without any additional air supply source. Instead,actuators 110 use the ambient air 600 to generate the pulsating flow ofair (by unsteady suction of blow of the air via cavity 512).

In actuators 110, an isolated synthetic jet is produced by the interactsof a train of vortices 606 that are typically formed by alternatingmomentary ejection and suction of fluid across jet orifice 514, suchthat the net mass flux is zero. Because synthetic jet 602 is formedentirely from the working fluid 600, actuators 110 can transfer linearmomentum to the flow system without net mass injection across the flowboundary.

Actuators 110 may produce synthetic jet 602 over a broad range of lengthand time scales. For example, a length scale of actuator 110 may bebetween about 6 mm by 1 mm to about 100 mm by 5 mm (for a rectangularjet orifice 514) and between about 1 mm diameter to about 20 mm diameter(for a circular jet orifice 514). The time scale may be, for example,from about 1/3000 second to about 1/10 second. The interaction ofsynthetic jets 602 with an external cross flow over the surface uponwhich actuators 110 are mounted may be used to displace localstreamlines (as shown in FIGS. 7A and 7B) and induce an apparent orvirtual change in the shape of the surface. In one example, syntheticjets 602 may affect flow changes on length scales that are one to twoorders of magnitude larger than the characteristic scale of syntheticjets 602.

It is desirable that the actuation frequency be high enough so that theinteraction domain between actuator 110 and the cross flow issubstantially invariant on a global time scale of the flow, such thatglobal effects such as changes in aerodynamic forces are effectivelydecoupled from the operating frequency of actuators 110. For example,the actuation frequency may include, without being limited to, betweenabout 10 Hz to about 2 kHz. The voltage range may include, without beinglimited to about 10 V to about 500 V.

Referring to FIGS. 7A-7D, examples of synthetic jet actuation effects onairflow around tractor 200 and trailer 400 are shown. In particular,FIG. 7A is a perspective view diagram of tractor 200 coupled to trailer400 and airflow 704 in tractor gap 700 without operation of airflowcontrol system 102; FIG. 7B is a perspective view diagram of tractor 200coupled to trailer 400 and airflow 706 in tractor gap 700 with operationof airflow control system 102; FIG. 7C is a perspective view diagram oftrailer 400 and airflow 712 behind trailer 400 without operation ofairflow control system 102; and FIG. 7D is a perspective view diagram oftrailer 400 and airflow 714 behind trailer 400 with operation of airflowcontrol system 102.

As shown in FIG. 7A, airflow 702 is directed around tractor 200 andenters tractor gap 700. Within tractor gap 700, airflow 704 is created,which exhibits unsteadiness and may contribute to increased aerodynamicdrag. As shown in FIG. 7B, when synthetic jets 212 are activated, thelocal streamlines in tractor gap 700 are displaced and are redirected asairflow 706 (with decreased unsteadiness).

As shown in FIG. 7C, airflow 710 is directed around trailer 400 andexits behind trailer 700. Behind trailer 400, airflow 712 is created,which exhibits unsteadiness and may contribute to increased aerodynamicdrag. As shown in FIG. 7D, when synthetic jets 212 are activated, thelocal streamlines behind trailer 400 are displaced and are redirected asairflow 714 (with decreased unsteadiness).

Referring to FIG. 8 (and to FIG. 1A), a flow chart is shown of anexample method of controlling airflow of a bluff-body shaped vehicle. Atstep 800, components of system 102 are initialized. For example,controller 106 may initiate collection of sensor data from sensor unit104, may initiate power manager 108 and/or may send an indication todriver interface 116 that system 102 is in operation.

At step 802, controller 106 may perform diagnostic control of componentsof system 102, to identify any problems that may require maintenance. Atstep 804, it is determined whether maintenance is necessary (based onstep 802).

When it is determined, at step 804, that maintenance is necessary, step804 proceeds to step 806. At step 806, a maintenance indication ispresented to the driver, for example, via driver interface 116.Although, in step 806, a maintenance indication is presented, airflowcontrol system 102 may continue to operate. Accordingly, in someexamples, step 806 may proceed to step 808. According to other examples,step 806 may also include terminating operation of system 102. Examplesof diagnostic control (step 802) is described further below with respectto FIG. 9.

When it is determined, at step 804, that maintenance is unnecessary,step 804 proceeds to step 808. At step 808, it is determined whether atrailer is attached to the vehicle 100. A trailer indication may bestored (for example, in storage 118) if it is determined that a traileris attached. Actuator 110 selection and/or the operational signalsupplied to actuators 110 (for various control modes 130-138) may bedependent upon whether the trailer is attached.

At optional step 810, the position of fairing device 114 (if it isincluded with system 102) is adjusted based on the trailer indication(step 808). The position of fairing device 114 may be adjusted manuallyor automatically by optional fairing servomotor 112. Optional step 810is described further below with respect to FIG. 10.

At step 812, it is determined whether the air speed (U) is greater thana predetermined velocity threshold (U_(MIN)). For example, controller106 may monitor velocity sensor data from velocity sensor(s) 122. In anexample embodiment, the predetermined velocity threshold is about 30 mphto about 60 mph.

When it is determined, at step 812, that the air speed is less than orequal to the predetermined threshold, step 812 proceeds to optional step814. At optional step 814, spray control may be performed by controller106. As described further below with respect to FIG. 12A, actuators 110in various actuator modules (such as actuator module 202 shown in FIG.2A or actuator module 402 shown in FIG. 4A) may be activated to redirectspray from rain away from vehicle 100 and/or to redirect spray away fromother vehicles moving along the path of vehicle 100.

When it is determined, at step 812, that the air speed is greater thanthe predetermined threshold, step 812 proceeds to optional step 816. Atoptional step 816, controller 106 may perform stability control 136, tomonitor and correct unstable movement of a portion of vehicle 100 (suchas on trailer 400 (FIG. 4A)). Step 816 is described further below withrespect to FIG. 11.

At step 818, controller 106 receives environmental sensor data (such astemperatures and/or humidity) from environmental sensor(s) 120 andperforms an analysis of the current environmental conditions. At step820, controller 106 selects an operation frequency and a voltageamplitude for the operational signals (electrical signals 150) to beapplied to actuators 110 based on the environmental conditions (e.g.,relative humidity and/or temperature). Controller 106 may also selectthe operational parameters for various actuators 110 based on whether atrailer is attached and/or the current air speed. At step 822, one ormore actuators 110 are operated in drag reduction control according tothe operational signals (determined in step 820).

In general, the operation frequency and amplitude for the oscillatingvoltage signal may be determined according to one or more predeterminedrelationships between relative humidity, temperature and outputsynthetic jet characteristics. The predetermined relationship may bebased on physical characteristics of actuator 110 (such as a size and/orshape of cavity 512, material properties of piezoelectric disc 508 aswell as the properties of the fluid itself). In some examples, theoperation frequency and amplitude may be determined from a look up tableaccording to the temperature and/or the relative humidity. In otherexamples, controller 106 may use a mathematical model that may correlatethe optimal frequency and amplitude with temperature and/or relativehumidity data received from environmental sensor(s) 120. In general,there is an empirical relationship between temperature/humidity andfrequency/amplitude. The relationship may be a function of thepiezoelectric disc material and the diameter of the piezoelectric disc508. As another example, a temperature range between about −30° F. toabout 113° F. and a relative humidity range between about 0% to about100% may correspond with an operation frequency between about 0 Hz toabout 3 kHz and an operation amplitude between about 10 V to about 500V.

At optional step 824, controller 106 may perform spray control incombination with drag reduction control. Step 824 is described furtherbelow with respect to FIG. 12B.

At optional step 826, controller 106 may optionally perform diagnosticcontrol 826, as described with respect to FIG. 9. Optional step 826 mayproceed to step 812, and steps 812-optional step 826 may be repeated aslong as system 102 is operational.

Referring to FIG. 9, a flow chart is shown of an example method ofperforming diagnostic control (step 802 and optional step 826 of FIG.8). At step 900, connected actuators 110 are detected, for example, byone or more current detectors (an example of diagnostic sensor 124)electrically coupled to actuators 110 via an electrical conduit. At step902, it is determined, for example, by controller 106, whether thecurrent absorbed by actuators 110 are within predetermined currentlimits, based on the value of the current detector(s). For example, fora power of about 10 W to about 20 W per piezoelectric disk 508 and avoltage amplitude of about 200 V, the predetermined current limits maybe between about 1.8 A to about 3.6 A (for a tractor having 36piezoelectric discs) and between about 2.7 A to about 5.4 A (for atrailer having 54 piezoelectric discs).

When it is determined, at step 902, that the absorbed current is outsideof the predetermined current limits, step 902 proceeds to step 904. Atstep 904, controller 106 performs a short-circuit analysis of theelectrical circuit (of actuators 110) based on the sensor data from thecurrent detector(s). At step 906, a location of a short-circuit in theelectrical circuit is determined by controller 106, based on theanalysis in step 904. At step 908, a maintenance indication is prompted,by controller 106. The maintenance indication may also be stored instorage 118. The stored maintenance indication may include informationregarding the short-circuit condition, including the identified locationof the short-circuit. The maintenance indication may also be provided tothe driver (as in step 806 of FIG. 8).

At step 910, responsive to the short-circuit condition, controller 910may terminate operation of system 102.

When it is determined, at step 902, that the absorbed current is withinthe predetermined current limits, step 902 proceeds to step 912. At step912, it is determined whether current absorption profiles of actuators110 are within predetermined tolerances. For example, controller 106,may monitor the absorption profile of actuators 110 (such as anamplitude of the profile) via one or more current detectors (an exampleof diagnostic sensor 124) coupled to actuators 110.

When it is determined, at step 912, that the absorption profiles areoutside of the predetermined tolerances, step 912 proceeds to step 914.At step 914, an actuator 110 is identified, by controller 106, as havinga clogged jet orifice 514 (FIG. 5A). At step 916, controller performs ajet de-clogging cycle for the identified actuator 110 (in step 914). Forexample, controller 106 may cause power manager 108 to operate theidentified actuator according to a predetermined operation frequencyand/or voltage amplitude, in an attempt to de-clog the jet orifice. Step916 proceeds to step 912.

When it is determined, at step 912, that the absorption profiles arewithin the predetermined tolerances, step 912 proceeds to step 918. Atstep 918, it is determined whether strain gauge signals of one or moreactuators 110 are within predetermined tolerances. For example,controller 106 may monitor strain gauge signals of strain gauges(examples of diagnostic sensor 124) mounted on piezoelectric discs 508FIG. 5A) of actuators 110. For example, when a piezoelectric disc 508 isoperating normally, the strain gauge signal may exhibit a sinusoidalshape. If piezoelectric disc 508 is cracked or broken, the strain gaugesignal may still be somewhat sinusoidal with a reduced amplitude or thesignal may be a flat line.

When it is determined, at step 918, that the strain gauge signals arewithin the predetermined tolerances, step 918 proceeds to step 808 orstep 812 (FIG. 8).

When it is determined, at step 918, that the strain gauge signals areoutside of the predetermined tolerances, step 918 proceeds to step 920.At step 920, controller 106 determines that a piezoelectric disc 508 isbroken. At step 922, controller 106 stores an indication, such as instorage 118, that the identified actuator cartridge 518 should bereplaced. At step 924, controller 106 regulates operation of theremaining functional actuators to compensate for the broken actuator.Step 924 proceeds to step 808 or to step 812.

Referring to FIG. 10, a flow chart is shown of an example method ofperforming jet angle control by adjusting the fairing position accordingto whether a trailer is attached (optional step 810 in FIG. 8). At step1000, it is determined, by controller 106, whether a trailer isattached, based on the trailer indication determined in step 808 (FIG.8).

When it is determined, at step 1000, that a trailer is not attached,step 1000 proceeds to step 1002. At step 1002, the fairing position isset (either manually or via fairing servomotor 112 by controller 106)for a tractor only position, such as the position shown in FIG. 3A. Inthis manner, the jet angle for synthetic jets 212 of actuators 110 onfairing device 114 may be adjusted inwards toward the tractor gap.

When it is determined, at step 1000, that a trailer is attached, step1000 proceeds to step 1004. At step 1004, controller 106 determines aproximity of the tractor to the trailer, such as from proximity sensordata of proximity sensor 128. At optional step 1006, controller 106 maydetect a trailer profile. For example, the driver may select the trailerprofile from among a list of predetermined trailer profiles, via driverinterface 116. As another example, controller 106 may detect the trailerprofile based on its coupling to the tractor, a weight of the trailer,etc. As a further example, controller 106 may detect the trailer profilebased on proximity sensor data from one or more proximity sensors 128(e.g., proximity sensors 128 acting as a radar system).

At step 1008, an optimal jet angle for synthetic jets 212 of actuators110 on fairing device 114 is set by controller 106, based on the trailerproximity (step 1004) and/or the trailer profile (optional step 1006).At step 1010 the fairing position is set (either manually or via fairingservomotor 112 by controller 106) for a trailer included position, suchas the position shown in FIG. 3B.

Referring to FIG. 11, a flow chart is shown of an example method ofcontrolling vehicle stability (optional step 816 in FIG. 8). At step1100, controller 106 determines the current vehicle stability conditionbased on one or more stability sensors 128 mounted on vehicle 100. Forexample, one or more stability sensors 128 such as a center of gravity,a weight and/or an accelerometer may be mounted on the vehicle body(such as a trailer) which may be prone to unstable movement (such asslipping).

At step 1102, the current condition (step 1100) is compared, bycontroller 106 to a predetermined optimal stability condition (which maybe stored in storage 118).

At step 1104, it is determined whether an instability is detected, bycontroller 106, based on the comparison in step 1102. When it isdetermined, at step 1104, that an instability is not detected, step 1104proceeds to step 818 (FIG. 8).

When it is determined, at step 1104, that an instability is detected,step 1104 proceeds to step 1106. At step 1106, controller 106 controlspower manager 108 to activate one or more actuators 110 to provide astabilizing net force on vehicle 100, based on the detected instability.For example, if the trailer slides to the left while vehicle 100 ismoving, some actuators 110 may be activated while other actuators 110may be terminated to cause the trailer to move in the opposite direction(i.e., to the right).

Step 1106 proceeds to step 1100, and steps 1100-1106 are repeated untilno further instabilities are detected.

Referring to FIGS. 12A and 12B, flow charts are shown of example methodsof performing spray control. In particular, FIG. 12A represents spraycontrol when vehicle 100 is moving at less than the predeterminedvelocity threshold (optional step 814); and FIG. 12 represents spraycontrol when vehicle 100 is moving at greater than the predeterminedvelocity threshold (optional step 824).

Referring to FIG. 12A, at step 1200, it is determined, by controller106, whether the spray control mode is active. When it is determinedthat the spray control mode is not active, step 1200 proceeds to step812 (FIG. 8).

When it is determined that the spray control mode is active, step 1200proceeds to step 1202. At step 1202, the controller 106 receivesenvironmental sensor data from environmental sensor(s) 120 (such asdirectly from a rain sensor a temperature sensor and/or a humiditysensor) and performs an analysis of the current environmental conditionsto detect rain.

At step 1204, it is determined, by controller 106, whether rain isdetected, based on the current environmental conditions (step 1202).When it is determined that rain is not detected, step 1204 proceeds tostep 812 (FIG. 8).

When it is determined that rain is detected, step 1204 proceeds to step1206. At step 1206, controller 106 controls operation of one or moreactuators associated with spray control. For example, actuators on atleast one of a rear of a tractor, a front of the tractor, a side of atrailer, a bottom of the trailer, a rear of the trailer, a wheel fenderof the tractor or a wheel fender of the trailer may be actuated forspray control. Step 1206 proceeds to step 1202.

Referring to FIG. 12B, at step 1210, it is determined, by controller106, whether the spray control mode is active. When it is determinedthat the spray control mode is not active, step 1210 proceeds tooptional step 826 (FIG. 8).

When it is determined that the spray control mode is active, step 1210proceeds to step 1212. At step 1212, the controller 106 receivesenvironmental sensor data from environmental sensor(s) 120 (such asdirectly from a rain sensor a temperature sensor and/or a humiditysensor) and performs an analysis of the current environmental conditionsto detect rain.

At step 1214, it is determined, by controller 106, whether rain isdetected, based on the current environmental conditions (step 1212).When it is determined that rain is not detected, step 1214 proceeds tooptional step 826 (FIG. 8).

When it is determined that rain is detected, step 1214 proceeds to step1216. At step 1216, controller 106 controllers operation of one or moreactuators associated with both spray control and drag reduction. Forexample, actuators on at least one of a rear of a tractor, a front ofthe tractor, a side of a trailer, a bottom of the trailer, a rear of thetrailer, a wheel fender of the tractor or a wheel fender of the trailermay be actuated for spray control and drag reduction. Step 1216 proceedsto step 1212.

Although the invention is illustrated and described herein withreference to specific embodiments, the invention is not intended to belimited to the details shown. Rather, various modifications may be madein the details within the scope and range of equivalents of the claimsand without departing from the invention.

What is claimed:
 1. A system for airflow control of a moving groundvehicle, the system comprising: an actuator module, mounted on thevehicle, having at least one synthetic jet actuator with at least an airinput configured to receive airflow around the moving ground vehicle,configured to generate a synthetic jet using the received airflow aroundthe moving ground vehicle, and with at least an air output configured tooutput the synthetic jet to modify the airflow around the moving groundvehicle; a sensor unit, mounted on the vehicle, having at least oneenvironment sensor configured to capture environmental sensor dataproximate the vehicle; and a controller configured to receive theenvironmental sensor data from the sensor unit and to determine at leastone of a drive frequency and a drive amplitude for controlling the atleast one synthetic jet actuator, based on the received environmentaldata.
 2. The system of claim 1, wherein the environmental sensorincludes at least one of a temperature sensor or a humidity sensor. 3.The system of claim 1, the system further comprising a power managerelectrically coupled to the at least one synthetic jet actuator, thepower manager configured to generate an oscillating voltage signal basedon the at least one of the drive frequency and the drive amplitudedetermined by the controller, the oscillating voltage signal being usedto drive the at least one synthetic jet actuator.
 4. The system of claim3, the system further comprising a mounting frame disposed on thevehicle, the actuator module configured to be coupled to the mountingframe, the mounting frame electrically connecting the at least onesynthetic jet actuator to the power manager.
 5. The system of claim 1,wherein the actuator module is configured to be detachably coupled tothe vehicle.
 6. The system of claim 1, wherein: the sensor unit includesat least one velocity sensor configured to capture velocity sensor dataof the vehicle, and the controller is configured to control operation ofthe at least one synthetic jet actuator when the captured velocitysensor data is greater than a predetermined velocity threshold.
 7. Thesystem of claim 1, wherein: the sensor unit includes at least onediagnostic sensor configured to capture diagnostic sensor dataassociated with the actuator module, and the controller is configured todetect a predetermined condition of the actuator module based on thediagnostic sensor data, the predetermined condition including at leastone of a predetermined mechanical condition or a predeterminedelectrical condition.
 8. The system of claim 7, further comprising adriver interface coupled to the controller, the driver interfaceconfigured to provide an indication of the detected predeterminedcondition to an occupant of the vehicle.
 9. The system of claim 1,further comprising a fairing device movably coupled to the vehicle, theactuator module being mounted on or integrated with the fairing device,the controller being configured to control adjustment of the fairingdevice to modify a direction of the generated synthetic jet.
 10. Thesystem of claim 9, wherein the vehicle includes a tractor coupled to atrailer and the sensor unit includes at least one proximity sensorconfigured to capture proximity sensor data of a proximity of thetractor to the trailer, and the controller is configured to control theadjustment of the fairing device based on the proximity sensor data. 11.The system of claim 1, wherein: the sensor unit includes at least onestability sensor configured to capture stability sensor data associatedwith movement of the vehicle, and the controller is configured to detectan unstable movement of the vehicle based on the stability sensor data,and to adjust operation of the at least one synthetic jet actuator toprovide a stabilizing net force on the vehicle.
 12. The system of claim1, wherein the controller is configured to detect a rain condition basedon the environmental sensor data, and to adjust operation of the atleast one synthetic jet actuator to control a spray direction of rainaround the vehicle.
 13. The system of claim 1, wherein the actuatormodule includes a plurality of actuator modules positioned at differentlocations on the vehicle, operation of each of the actuator modulesbeing independently controlled by the controller.
 14. A method forairflow control of a moving ground vehicle, the method comprising:capturing environmental sensor data proximate the vehicle from anenvironmental sensor mounted on the vehicle; determining, by acontroller, at least one of a drive frequency and a drive amplitude forcontrolling at least one synthetic jet actuator mounted on the vehicle,based on the received environmental data; and generating a synthetic jetby the at least one synthetic jet actuator using airflow around themoving ground vehicle based on the at least one of the drive frequencyand the drive amplitude, and outputting the synthetic jet to modify theairflow around the moving ground vehicle.
 15. The method of claim 14,the method further comprising: capturing velocity sensor data of thevehicle by at least one velocity sensor mounted on the vehicle; andcontrolling, by the controller, operation of the at least one syntheticjet actuator when the captured velocity sensor data is greater than apredetermined velocity threshold.
 16. The method of claim 14, the methodfurther comprising: capturing diagnostic sensor data associated with theat least one synthetic jet actuator by at least one diagnostic sensor;and detecting, by the controller, a predetermined condition of the atleast one synthetic jet actuator based on the diagnostic sensor data,the predetermined condition including at least one of a predeterminedmechanical condition or a predetermined electrical condition.
 17. Themethod of claim 14, wherein the at least one synthetic jet actuator ismounted on or integrated with a fairing device, the fairing devicemovably coupled to the vehicle, the method including: controlling, bythe controller, adjustment of the fairing device to modify a directionof the generated synthetic jet of the at least one synthetic jetactuator.
 18. The method of claim 17, wherein the vehicle includes atractor coupled to a trailer and the method further comprises: capturingproximity sensor data of a proximity of the tractor to the trailer fromat least one proximity sensor mounted on the vehicle; and controlling,by the controller, the adjustment of the fairing device based on theproximity sensor data.
 19. The method of claim 14, the method furthercomprising: capturing stability sensor data associated with movement ofthe vehicle from at least one stability sensor mounted on the vehicle;detecting, by the controller, an unstable movement of the vehicle basedon the stability sensor data; and adjusting operation of the at leastone synthetic jet actuator to provide a stabilizing net force on thevehicle.
 20. The method of claim 14, the method further comprising:detecting, by the controller, a rain condition based on theenvironmental sensor data; and adjusting operation of the at least onesynthetic jet actuator to control a spray direction of rain around thevehicle.